You all debating about ketchup on spaghetti when what's really important is how creative Kiyo was to have the mini picnic on the balcony so that Sumire wouldn't be upset. It's just a light coating and is usually mixed with tonkotsu or worcestershire sauce depending on the restaurant/household. And if you all think ketchup on spaghetti is weird, Japan probably thinks something similar about avocado sushi.